Ppm questions

[RatmanOG]

hey folks, i have a question about ppm in regards to run off. i’ll tell you a little about my grow first, i have 5 plants growing in coco and perlite, feeding with remo nutrients, growing in a DIY greenhouse. pretty much feeding every other day, but i decided to let my plants go an extra day before watering because algae had formed on top of the perlite. my nute strength is typically 600-700 ppm and my run off is usually just a little bit higher than that. but today when i fertigated, the run off was testing at around 450-700 which is a few hundred points below what it normally is when i test the run off (after feeding every second day). my understanding is the ppm of the run off should always be higher than the nutrients being added to the medium, because as the nutes sit in the coco, the salt concentration in the medium increases as the water is drawn out by the plant roots

my plants are pretty healthy, the largest one has early stage Calmag deficiency but that’s about the only issue

[Toker1]

Ppm is an abbreviation for particles per million. Plus or minus a few hundred is basically negligible when speaking in terms of millions.

[RatmanOG]

good point at that sir. i figured the ppm would be much higher after having extra time for the roots to absorb the nutrients

[Toker1]

Absorbed nutrients would subtract from the total ppm. Adding nutrients is the same as adding more particles.